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All the reading says though is that "participants report being more energetic and alert on average than the average level reported by the National Institute of Health survey for all Americans". It does not say that participants report being more energetic and alert than before they took the pill. Technically, if they only had participants who started off well above the national average, and if in fact, participants' energy on average declined, but declined such that they were still above the national average, the advertisement's claim would still be true, though definitely wouldn't strengthen.

"E" does not point out that people's energy levels definitely increased. It only points out that people who took cellulose didn't feel an increase. We have no idea if anyone even felt an increase in energy levels. One scenario could be that the participants started off on average above the national baseline, and no one felt any increase in energy levels, regardless of being fed cellulose or not. In this scenario, E would be true, participants fed cellulose didn't report any increase, and the reading would still be true, which is that participants on average were more alert than the national baseline (but only because they started off above already!).

"C" to me takes the guesswork out of the equation. Because everyone in the study started off no better than the national average, it implies that the pills brought study participants above the national average. Of course, there could be external non-pill related factors at play, but "C" to me eliminates a lot of the guesswork around whether the study was rigged etc.

Hi

Kindly refer to below issues in C
1. It speaks about alertness only and not energetic
2. Most Important is to note here that: In C it says that the "average" of the participants alertness level was similar to national average. Here one can clearly infer that the few participants had above average alertness level while others had lower. So the representative sample of participants is not correct.


While in E
1. The option has clarified that other substance was not able to increase the level of alertness showing that 1. Vita plus is better 2.It can be inferred that the since other substance did not increase the performance the actual level of performance was known or low enough.

In conclusion the Process of elimination is the best approach to handle such question so we can identify the best strengthener


Regards

IMO answer should be E.
We need to strengthen the claim that taking 2 capsules of vita plus supplements make one "both"energetic and alert.


(A) Those who voluntarily chose to take more than 2 capsules daily reported energy levels even greater than those who took only 2 capsules. Does not say that 2 capsules would make one more energetic. More than 2 are surely more energetic.
(B) The volunteers were randomly selected from all those who answered a newspaper advertisement and were willing to pay for the cost of the Vita-Plus capsules. - Does not strengthen the claim. OOS.
(C) At the beginning of the study, the volunteers’ reports on alertness showed levels on average no different from the average level reported by the National Institutes of Health. - There were no difference in alertness but there can be difference in energy levels. The argument would fall apart if this was the case. Surely doesn't strengthen.
(D) Some of the volunteers were given capsules that solely contained cellulose, an inert substance with no vitamins or other health inducing substances. Those volunteers also reported increased levels of alertness and energy. Weakens the conclusion.
(E) Some of the volunteers were given capsules that solely contained cellulose, an inert substance with no vitamins or other health inducing substances. Those volunteers reported no increase in alertness or energy. - This seems right because it says cellulose cannot increase levels of alertness and energy. Hence it must be vitamin, which is present in supplements.

I understand C talks only about alertness but still it partly strength end the argument. At the same time E implies: no vitamin -> no increase, therefore the observed increase is because of the vitamin. This correlation cannot establish causal relationship. I feel C strengthens more than E does, by eliminating the possibility that the sample itself is biased.

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(C) At the beginning of the study, the volunteers’ reports on alertness showed levels on average no different from the average level reported by the National Institutes of Health.

(E) Some of the volunteers were given capsules that solely contained cellulose, an inert substance with no vitamins or other health inducing substances. Those volunteers reported no increase in alertness or energy.

Between C and E

Option C only tells us that volunteers alertness levels were very similar to general population. We cannot conclude that capsules are the reason for increased alertness. There may be others reasons for alertness.

Option E- this choice gives us a reason to believe that capsules are the cause of alertness. The volunteers who did not receive the capsules showed no increase in alertness levels whereas volunteers who were given capsules showed increased alertness ( From Premise).
Option E adds new additional information,which strengthens the conclusion.

Pattern X --------> Y

Conc : Have my pill to feel active / energetic.
Asumpt : My Pill actually works and fills you with a lot of energy
Pre think : What if 1) Something else causes this increase . 2) NIHS data is represntative for all americans.
What to look for 1) Y-----> X (should not happen) 2) No X --- No Y 3) Eliminate other causes.

Between C and E


C : At the beginning of the study, the volunteers’ reports on alertness showed levels on average no different from the average level reported by the National Institutes of Health. Try negating (Simple english negating not playing with keywords and all , maybe the correct word is falsifying) : No different has two aspects :
1 That the average level of alertness of volunteers was much lesser. ------> Even if it was much lesser, we can say that it increased by pills. This case strengthens.
2 The average level of volunteers was already too high ----> NIHS data is not representative ----> Prethink 2 -----> Pills had nothing to do with this, levels were already high. This case weakens.

All in, C presents a dichotmoy. OUT

(E) Some of the volunteers were given capsules that solely contained cellulose, an inert substance with no vitamins or other health inducing substances. Those volunteers reported no increase in alertness or energy.
Simple logic No Y ------> No X.

A- I eliminated A on seeing it but can somebody please explain me in detail why we need to eliminate A. Is it that experiment is only concerned about only 2 capsule in a day.

B- OFS, nothing do with the conclusion

C- Only alertness is discussed, but if we see the premise of the argument than we find out that in the first line its clearly mentioned energetic...etc etc... so we can eliminate C

D- We can support a conclusion only when we have proof that in the absence of those capsule the effect is gone. Like in causality question.

Cause – Taking 2 capsule

Result- More energetic

So when Cause absence effeect also absence like mention in "e".
But in D we have different cause than that miight be have same or different result.


Please check and Confirm whether my reasoning is correct or not.

Also shed some light on option "A"

E: Volunteers that were given capsules that solely contained cellulose reported no increase in alertness or energy. This answer does not tell us whether the participants who took Vita-Plus reported an increase in alertness or energy. They may initially have had a higher level of alertness and energy than the average level reported by the National Institutes of Health survey of all Americans.
The stimulus compares the level of the participants with the average national level, while the conclusion refers to the increment in the level of the users. We know that the level of the participants is higher than the average, but we do not know whether there was an increment in the level.

C: Eliminates a possible bias in the sample. If the participants did not initially have a higher level than average, we can infer that there was an increment in the level. Even if it only refers to alertness, it supports the claim.

Answer: C

NOVA is not a good source for GMAT questions.